LICENSE: update to include @vscode/codicons license notice

For #2525

It's generated by tools/license.sh that runs:

yarn licenses generate-disclaimer --prod

Change-Id: Ic09652ec3c67becb75ca5ef0362e509365f39280
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/447262
TryBot-Result: kokoro <[email protected]>
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: hyangah